Tandem packing for a reciprocating pump

ABSTRACT

A packing assembly for a pump includes a pair of packings arranged in tandem along the plunger of a reciprocating pump or along the shaft of a centrifugal pump to provide axially-spaced sealing intervals. The tandem packing arrangement permits the pump to be operated through two stages, with separate packings providing the seal in each stage.

United States Patent [1 1 Maurer et al.

TANDEM PACKING FOR A RECIPROCATING PUMP Inventors: William C. Maui-er,Houston; Joe K.

Heilhecker, Bellaire; Everett H. Lock, Houston, all of Tex.

Esso Production Research Company, Houston, Tex.

Filed: Mar. 17, 1972 Appl. No.: 235,514

Assignee:

U.S. Cl 277/9, 277/58, 277/71, 92/165 Int. Cl F16j 15/18 Field of Search277/3, 9, 2, 16, 277/32, 58, 59, 70, 71, 72, 74; 92/165 References CitedUNITED STATES PATENTS 3/1954 Tremolada 277/32 Dec. 4, 1973 3,514,1145/1970 Monahan 277/3 Primary ExaminerWilliam T. Dixson, Jr. AssistantExaminer-Robert L Smith Att0rneyJames A. Reilly et a1.

[5 7] ABSTRACT A packing assembly for a pump includes a pair of packingsarranged in tandem along the plunger of a reciprocating pump or alongthe shaft of a centrifugal pump to provide axially-spaced sealingintervals. The tandem packing arrangement permits the pump to beoperated through two stages, with separate packings providing the sealin each stage.

9 Claims, 1 Drawing Figure TANDEM PACKING FOR A RECIPROCATING PUMPBACKGROUND OF THE INVENTION 1. Field of the Invention:

This invention relates to packings for pumps.

2. Description of the Prior Art:

A major problem associated with high-pressure pumps is that of providinga satisfactory seal for the plunger of a reciprocating pump or the shaftof a centrifugal pump. The seal is normally in the form of soft,non-abrasive packing adapted to seal the radial space between the pumpplunger (or shaft) and the fluid end housing. The failure of the packingis a particularly serious problem when the fluid being pumped containssuspended particles of silt, clay, sand or a similar abrasive material.The abrasive material tends to erode the packing, causing early andfrequent failure.

Packing failure is normally evidenced by the leakage of fluid past thepacking. A small amount of leakage can be tolerated but when thisbecomes excessive, the pumping operations must be temporarilydiscontinued to permit replacement of the packing. In certain processes,it may be inconvenient and sometimes may even jeopardize the success ofthe process to interrupt pumping operations immediately upon packingfailure. Two examples of processes that cannot tolerate long shutdownperiods are found in well drilling and well fracturing operations. Inthe drilling of wells by rotary drilling methods, a drilling fluid iscontinuously circulated through a tubular drill string and servesseveral essential functions in the drilling operation. It .is desirableto perform maintenance and repair work on the drilling pumps when thecirculation of the drilling fluid in the well is not required. This workis normally done at the same time the drill bit is being replaced, whichrequires withdrawing the entire drill string from the bore-hole. Thisoperation normally requires several hours and thus provides ample timefor pump maintenance and repair. The pump packing frequently failsbefore the bit has become sufficiently worn to require replacement. Inthis event, it is desirable to delay repacking the pump until the bitmust be withdrawn from the borehole. However, with most conventionalpumps, the packing must be replaced immediately upon packing failure.

Well fracturing normally involves the injection of a fluid into asubterranean formation at a pressure sufficient to open a fracturetherein and the placement of propping agent particles in the fracture.The propping agent particles suspended in the fracturing fluid arecarried to and deposited in the fracture. The fracturing fluid must bepumped into a subterranean formation at a sufficiently high velocity toprevent the propping agent particles from settling. During thisoperation, if pumping is interrupted even for a short period of time,the particulate material tends to settle in the borehole and plug theformation. Here again, it is desirable to delay repacking the pump untilthe process has been completed.

SUMMARY OF THE INVENTION The present invention provides an improvedpacking assembly for pumps. It should be noted that the term pump refersto any mechanical device used to raise, transfer, or compress fluids andspecifically includes reciprocating pumps, centrifugal pumps,compressors,

and hydraulic rams. Briefly, the improved packing assembly includes twosets of packings-an inner packing and an outer packing-designed toseparately provide a seal for the pump plunger or shaft. The separatepackings are arranged in tandem and provide a sea] at axially-spacedintervals. A novel feature of this design is that the separate packingscan be used in sequence so that the operating life of the packing can beextended even after one of the packings has failed. A support member isprovided between the packings and serves to bear the hydraulic loadingimposed on the inner packing. A vent port communicates with the axialspace separating the two packings so that fluid leaking past the innerpacking is vented to the atmosphere. Thus, it is seen that the outerpacking is not hydraulically loaded during the initial stage ofoperation. When leakage past the inner packing becomes excessive, theouter packing can be activated merely by closing the vent port. Thiscauses the buildup of pressure in the axial space separting the twopackings. The resultant hydraulic loading on the outer packing deformsthe packing elements thereof into engagement with the surfaces beingsealed.

The packing assembly preferably is in the form of an insert cartridgeadapted to be connected to the fluid end housing. The cartridge includesa sleeve containing the two sets of packings. Formed in the sleeve is avent port for relieving the pressure between the packings, and passagesfor delivering lubricant, coolant, or a wash fluid to the packings. Thecartridge design permits rapid replacement of the packing since thesleeve and packings can be withdrawn from the fluid end housing as aunit and replaced with a new unit.

BRIEF DESCRIPTION OF THE DRAWING The drawing schematically illustrates,in longitudinal section, a portion of a pump containing a packingassembly constructed according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The prsent invention will bedescribed with reference to a reciprocating pump. It should be realized,however, that the improved packing can also be used in centrifugalpumps, compressors, hydraulic rams and the like. In all of thesedevices, a member such as a plunger or shaft is movably mounted in ahousing. The packing serves to seal the radial space between the housingand the movable member.

As shown in the drawing, the fluid end of a reciprocating pump comprisesseparate steel forgings which include a fluid end housing 10 mounted onpump frame 11 and a crossbore body, shown partially as 12, coupled tothe housing 10. The crossbore body 12 can be similar in structure tothat disclosed in assignees copending Application Ser. No. 179,705,filed September 13, 1971. Other structures my also be employed. The

ing action draws fluid into the pump fluid end and discharges it at highpressures. in order to seal the annular space between the plunger andhousing 10, a packing is normally provided in an end section of thehousing 10.

The plunger packing in accordance with the present invention is providedby two separate packings arranged in tandem along the pump plunger. Thisarrangement provides separate seals at axially-spaced intervals andpermits the pump to be operated through two stages before the packingmust be replaced. In the preferred embodiment, the plunger packing is inthe form of a packing cartridge 17 adapted to be installed on the pumpfluid end. However, it will be apparent from the following detaileddescription that the tandem packing arrangement is not restricted to thecartridge design.

At the rear extremity of the fluid end housing 10, the bore 14 isenlarged, as by a counterbore, to provide an annular recess in thehousing 10. The recess is sized to receive the cartridge 17 and isdefined by radial surface 18 and a cylindrical surface 19. An interallythreaded section 20 is provided at the mouth of the recess. The innerextremity of the recess, defined by surface 18, is disposed sufficientlyclose to the front end of the plunger 15 in its fully retracted positionto permit the plunger 15 to be tilted sufficiently to place its rear endradially clear of the front end of the drive rod 16. This distancenormally will be less than about one inch. As described in more detailbelow, thisarrangement permits the packing to be replaced withoutremoving a pony rod section from the drive rod 16.

The packing cartridge 17 includes a sleeve 21 and a pair of packings 22and 23 mounted in the sleeve 21. The sleeve 21 may be constructed fromstandard steel bar stock. A bar of the proper length is bored to form anaxial opening therethrougha portion of the opening is shown as 24andthen counterbored to form enlarged sections 25 and 26. These sectionsextend from opposite ends inwardly into the bar and terminate a shortaxial distance apart leaving an annular shoulder 27 therebetween. Theouter periphery of the bar is machined to provide the sleeve 21 with athreaded section 28 and a cylindrical section 29. The threads of section28 mate with the housing threads 20, and the cylindrical section 29 fitsin close conformity with the internal surface 19 of housing 10. Aforward end of the sleeve 21 carries a face seal such as an elastomericO-ring 30.

With the sleeve 21 mounted on the housing 10, its forward end containingthe face seal 30 is disposed internally of the housing 10. The face seal30 is compressed into sealing engagement with the radial surface -18formed in the housing 10. The outer end 31 of the sleeve 21 is exposedand may be provided with a hex head or similar structure sized to fit awrench.

The packings 22 and 23, respectively, fit in the enlarged sections 25and 26 of the sleeve 21. The outer packing 22 may include a plurality ofseal rings 32, an adaptor 33 and a lantern ring 34. It is preferred thatthe packing 22 also include a compression spring 35 for maintaining aminimum force on the ring assembly. One end of the spring 35 engages theannular shoulder 27 and the opposite end through a spring adaptor 36applies a force on the stackup of rings. This entire assembly ismaintained within the enlarged section 25 by a nut 37 threadedlyconnected to the outer end 31 of the sleeve 21.

The inner packing 23 may be similar in construction as assembly 22comprising seal rings 38, adaptor 39, lantern ring 40, compressionspring 41, and spring adaptors 42 and 43. The rings 38, 39, 40 and 42arranged in stacked relation and preloaded by spring 41 are supportedwithin the enlarged section 26 on an annular shoulder 27.

With the sleeve 21 attached to the fluid end housing 10 and insurrounding relation to the plunger 15, the enlarged sections 25 and 26in combination with the outer periphery of the plunger 15 define annularspaces. The packings 22 and 23 mounted in the sleeve 21 provide sealsfor these spaces. The sealing intervals are separated by an axial spaceindicated at 44. A vent port 46 formed in the sleeve 21 communicateswith the axial space 44. The vent port 46 extends from the sleeve outerend 31 axially through a portion thereof and into enlarged section 25.The compression spring 35 maintains the rings clear of the vent port 46.Means are provided for selectively closing the vent port. A plug 51adapted to be screwed into a threaded outlet 45 of the vent port 46 maybe used for this purpose. Alternatively, a valve connected in fluidcommunication with the vent port 46 may be used.

The lantern rings 34 and 40 of packings 22 and 23 are flanked on eitherside by a plurality of seal rings. Lubricating passages 47 and 48 formedin the sleeve 21 serve to deliver lubricant to the packings 22 and 23,respectively. Each of the lubricating passages 47 and 48 has an inlet atthe outer end 31 of sleeve 21, and has an outlet in fluid communicationwith one of the lantern rings 34 and 40. A lubricating pump, not shown,is connected to each of the passages 47 and 48 and delivers a suitablelubricant such as oil to the packings 22 and 23.

When the fluid to be pumped is corrosive or contains abrasive material,the sleeve 21 can be provided with another passage 49 for delivering awash fluid to the pressure side of the inner packing 23. Passage 49 hasan inlet at the outer end 31 of the sleeve 21 and an outlet in fluidcommunication with the interior of the sleeve 21 at a point in advanceof the packing rings of assembly 23. A pump (not shown) connected topassage 49 delivers a wash fluid such as water to flood the pressureside of the packing assembly 23. Passage 49 may also be used to delivera coolant to the interior of sleeve 21 if desired.

The seal rings 32 and 38 are preferably of the selfenergizing type. Theymay be conventional V rings, U rings, W rings, and the like. These ringsare normally molded rings of elastomeric material containing fibrousreinforcement. The self-energizing seal rings are provided with lipsthat deform under hydraulic loading into sealing engagement with thesurfaces being sealed.

In assembling the cartridge 17, the outer packing 22 is inserted intothe sleeve 21. The nut 37 is then screwed into the sleeve end 31compressing the spring 35. The inner packing 23 is then placed in theenlarged section 26 of sleeve 21. The spring retainer 43 is placed inadvance of the compression spring 35 and serves to maintain thecompression spring in proper alignment. The cartridge 17 is thentelescopically positioned about the plunger 15 and directed into therecess end of housing 10. The sleeve 21 is screwed into the housing 10until the face seal 30 abuts the radial surface 18 formed in the housing10. It should be noted that the face seal 30 is compressed sufficientlyto provide a pressurized barrier at the joint of the members beingassembled. Screwing the sleeve 21 into the housing also compresses thespring 41 to provide a preload force on the rings 38, 39, 40 and 42.

An alternate procedure for installing the cartridge 17 on the pump fluidend is to preassemble the cartridge 17 and a plunger 15. The wornplunger and packing are then withdrawn as a unit from the pump andreplaced with a new assembly. It should be noted that the plunger orpacking can be replaced without disconnecting a pony rod section fromthe drive rod 16. This is possible because the recessed end of thehousing 10 permits the plunger to be tilted sufficiently such that itsouter end radially clears the front end of the drive rod 16. The mouthof the bore 14 at 50 may be enlarged slightly to facilitate the tiltingof the plunger 15.

With the cartridge 17 properly installed on the housing 10, the pump maybe operated through two stages with the inner packing 23 providing theplunger seal during an initial stage and the outer packing 22 providingthe plunger seal in a subsequent stage. In the initial stage, the ventport 46 is left open so that fluid leaking past the inner packing 23 isdischarged to the atmosphere. This prevents the buildup of pressure inthe space 44 separating the packings 22 and 23. In the absence ofpressure in this space, the outer packing 22 will not be deformed andtherefore will not be subjected to severe wear. It should be noted thatthe preloading afforded by the compression spring 35 is smallin theorder of 190 poundsand merely serves to maintain the rings in a tightlypacked condition. This preload force is negligible compared to thehydraulic loading of the pressurized fluid. For example, the hydraulicloading on 3% ID. X 4% OD. packing of a pump operating at 10,000 psi is62,800 pounds.

Annular shoulder 27 bears the hydraulic load imposed on the innerpacking 23 and prevents this load from being transmitted to packing 22.The pump may be operated through the initial stage until the seal ringsof the inner packing 23 fail. This will be evidenced by the discharge offluid from the vent port 46. The vent port 46 is then closed as byinserting a plug in end 45 permitting the pump to be operated through asecond stage wherein the plunger seal is provided by the outer packing22. Closing the vent port 46 causes the pressure to increase with space44. The buildup of pressure in this space energizes the seal rings 32 ofassembly 23. The pump then may be operated until the outer packing 23fails.

Alternatively, the vent port can be connected to a pump which delivers acoolant or wash fluid to the pressure side of packing 22.

Although the tandem packing arrangement of the present invention isdisclosed herein with reference to the cartridge 17, it should be notedthat other designs are possible. For example, the inner packing 23 canbe provided directly between a plunger and the housing 10. The outerpacking 22 may be mounted in a sleeve which is adapted to be attached tothe housing 10. This sleeve may be constructed to provide a supportcomparable to annular shoulder 27 described above for bearing thehydraulic loading imposed on the inner packing 23. Whether the designcalls for a cartridge or not, the ultimate function of the packings isthe same: to seal the enlarged annular space between the plunger 15 andhousing 10. In this regard, it should be noted that the cartridgeattached to the housing may be viewed as a part thereof.

The advantages of the tandem packing arrangement can be more fullyappreciated when viewed with reference to well drilling or wellfracturing operations discussed above. Assuming that drilling operationsare in progress, it is essential that drilling fluid be circulatedthrough the drill string. In the event that the inner packing 23 fails,the second packing 22 can be activated merely by closing the vent port46. This can be accomplished without interrupting the drilling operations and permits continued drilling until the drill bit becomessufiiciently worn to require replacement. The tandem packing arrangementnot only improves the efficiency of the operation but under certainconditions avoids hazards resulting from interrupting pumpingoperations. For example, it is undesirable to interrupt pumpingoperations for long periods of time because of the danger of stickingthe drill pipe.

In fracturing operations, the tandem packing ar' rangement of thepresent invention permits completion of pumping operations. For example,if the fluid laden with particulate material is being pumped and theinner packing 23 fails, the pumping operations may be continued merelyby closing the vent port 46 which activates the outer packing 22. Thelife of the outer packing 22 which has not been subjected to as severewear as the inner packing 23 is well within the time required tocomplete the pumping operations.

As mentioned previously, the improved packing of the present inventioncan be used on reciprocating pumps, centrifugal pumps, compressors, andsimilar devices. Its preferred application, however, is in reciprocatingpumps because of the serious packing problems associated with this typeof pump.

We claim:

1. A replaceable packing cartridge for sealing the annular space betweena pump housing and a moveable member which comprises: a sleeve adaptedto be detachably mounted to said housing in surrounding relation to saidmember and having an outer exposed portion and an inner end disposedadjacent said housing, said sleeve containing inner and outer packingassemblies and means for separately supporting said packing assemblies,said sleeve having formed therein a vent passage which extends from saidexposed portion to the interior of said sleeve at a point between saidpacking assemblies; and means for selectively closing said vent passagewhereby said pump in which said packing cartridge is mounted may beoperated through a first stage with the vent passage open wherein theinner packing assembly provides the seal for said annular space and asecond stage with the vent passage closed wherein the outer packingassembly provides the seal for said annular space.

2. A packing cartridge as defined in claim 1 wherein said inner packingassembly includes a plurality of selfenergizing seal rings and a lanternring interposed between two of said seal rings, and said sleeve hasformed therein a lubricating passage which extends from said exposedportion to the interior of said sleeve and is in fluid communicationwith said lantern ring.

3. A packing cartridge as defined in claim 2 wherein said sleeve hasformed therein a third passage for conducting a wash fluid which extendsfrom said exposed portion to the interior of said sleeve at a point inadvance of the seal rings of said inner packing.

4. A packing cartridge as defined in claim 3 wherein said sleeveincludes a face seal between said inner end and the adjacent housing.

5. A replaceable packing cartridge for sealing the annular space betweena pump housing and a pump plunger which comprises: a sleeve adapted tobe detachably mounted on said housing in surrounding relation to saidplunger and having an outer exposed portion and an inner end disposedadjacent said housing, said sleeve having formed therein an innerpacking chamber and an outer packing chamber separated by a supportshoulder; inner and outer packing assemblies mounted in said inner andouter packing chambers, respectively, each of said packing assembliesincluding a plurality of self-energizing seal rings, said inner packingassembly further including a lantern ring positioned between two of saidseal rings thereof, said sleeve having formed therein a lubricatingpassage which extends from said exposed portion to said inner chamberand being in fluid communication with said lantern ring, and a ventpassage which extends from said exposed portion and being in fluidcommunication with the interior of said sleeve at a point between theseal rings of said inner and outer packing assemblies; and means forselectively closing said vent passage whereby said pump containing saidpacking cartridge may be oper ated through a first stage with said ventpassage open wherein said inner packing provides the plunger seal andthrough a second stage with said vent passage closed wherein said outerpacking provides the plunger seal.

6. A packing cartridge as defined in claim 5 wherein said inner packingassembly further includes a spring for maintaining the rings of saidinner packing in compression.

7. A packing cartridge as defined in claim 6 wherein said sleeve hasformed therein a flow passage for conducting a wash fluid which extendsfrom said exposed portion to said inner chamber at a point opposite saidspring.

8. A packing cartridge as defined in claim 5 wherein said outer packingassembly further includes a lantern ring interposed between two of saidseal rings thereof and said sleeve has formed therein a secondlubricating passage which extends from said exposed portion to saidouter chamber in fluid communication with said lantern ring of saidouter packing.

9. A packing cartridge as defined in claim 5 wherein said inner andouter packing assemblies each include a spring for maintaining the ringsthereof in compression. l=

1. A replaceable packing cartridge for sealing the annular spAce betweena pump housing and a moveable member which comprises: a sleeve adaptedto be detachably mounted to said housing in surrounding relation to saidmember and having an outer exposed portion and an inner end disposedadjacent said housing, said sleeve containing inner and outer packingassemblies and means for separately supporting said packing assemblies,said sleeve having formed therein a vent passage which extends from saidexposed portion to the interior of said sleeve at a point between saidpacking assemblies; and means for selectively closing said vent passagewhereby said pump in which said packing cartridge is mounted may beoperated through a first stage with the vent passage open wherein theinner packing assembly provides the seal for said annular space and asecond stage with the vent passage closed wherein the outer packingassembly provides the seal for said annular space.
 2. A packingcartridge as defined in claim 1 wherein said inner packing assemblyincludes a plurality of self-energizing seal rings and a lantern ringinterposed between two of said seal rings, and said sleeve has formedtherein a lubricating passage which extends from said exposed portion tothe interior of said sleeve and is in fluid communication with saidlantern ring.
 3. A packing cartridge as defined in claim 2 wherein saidsleeve has formed therein a third passage for conducting a wash fluidwhich extends from said exposed portion to the interior of said sleeveat a point in advance of the seal rings of said inner packing.
 4. Apacking cartridge as defined in claim 3 wherein said sleeve includes aface seal between said inner end and the adjacent housing.
 5. Areplaceable packing cartridge for sealing the annular space between apump housing and a pump plunger which comprises: a sleeve adapted to bedetachably mounted on said housing in surrounding relation to saidplunger and having an outer exposed portion and an inner end disposedadjacent said housing, said sleeve having formed therein an innerpacking chamber and an outer packing chamber separated by a supportshoulder; inner and outer packing assemblies mounted in said inner andouter packing chambers, respectively, each of said packing assembliesincluding a plurality of self-energizing seal rings, said inner packingassembly further including a lantern ring positioned between two of saidseal rings thereof, said sleeve having formed therein a lubricatingpassage which extends from said exposed portion to said inner chamberand being in fluid communication with said lantern ring, and a ventpassage which extends from said exposed portion and being in fluidcommunication with the interior of said sleeve at a point between theseal rings of said inner and outer packing assemblies; and means forselectively closing said vent passage whereby said pump containing saidpacking cartridge may be operated through a first stage with said ventpassage open wherein said inner packing provides the plunger seal andthrough a second stage with said vent passage closed wherein said outerpacking provides the plunger seal.
 6. A packing cartridge as defined inclaim 5 wherein said inner packing assembly further includes a springfor maintaining the rings of said inner packing in compression.
 7. Apacking cartridge as defined in claim 6 wherein said sleeve has formedtherein a flow passage for conducting a wash fluid which extends fromsaid exposed portion to said inner chamber at a point opposite saidspring.
 8. A packing cartridge as defined in claim 5 wherein said outerpacking assembly further includes a lantern ring interposed between twoof said seal rings thereof and said sleeve has formed therein a secondlubricating passage which extends from said exposed portion to saidouter chamber in fluid communication with said lantern ring of saidouter packing.
 9. A packing cartridge as defined in claim 5 wherein saidinner and outer packing assemblies each include a spring for maintainingthe rings thereof in comPression.